Current issue: 56(2)
Under compilation: 56(3)
The productivity of Scots pine (Pinus sylvestris L.) under changing climatic conditions in the southern part of Finland was studied by scenario analysis with a gap-type forest ecosystem model. Standard simulations with the model predicted an increased rate of growth and hence increased productivity as a result of climatic warming. The gap-type model was refined by introducing an overwintering sub-model describing the annual growth cycle, frost hardiness, and frost damage of the trees. Simulations with the refined gap-type model produced results conflicting with those of the standard simulation, i.e., drastically decreased productivity caused by mortality and growth-reducing damage due to premature dehardening in the changing climate. The overwintering sub-model was tested with frost hardiness data from Scots pine saplings growing at their natural site 1) under natural conditions and 2) under elevated temperature condition, both in open-top chambers. The model predicted the frost hardiness dynamics quite accurately for the natural conditions while underestimating the frost hardiness of the saplings for the elevated temperature conditions. These findings show that 1) the overwintering sub-model requires further development, and 2) the possible reduction of productivity caused by frost damage in a changing climate is less drastic than predicted in the scenario analysis. The results as a whole demonstrated the need to consider the overwintering of trees in scenario analysis carried out with ecosystem model for boreal conditions. More generally, the results revealed a problem that exists in scenario analysis with ecological models: the accuracy of a model in predicting the ecosystem functioning under present climatic condition does not guarantee the realism of the model, nor for this reason the accuracy for predicting the ecosystem functioning under changing climatic conditions. This finding calls for the continuous rigorous experimental testing of ecological models used for assessing the ecological implications of climatic change.
BOREAS is a four-year, regional-scale experiment to study the forested continental interior of Canada. It aims at improving our understanding of the interaction between the earths' climate system and the boreal forests at short and intermediate time scales, in order to clarify their role in global change.
During the winter, spring and summer of 1994, five field campaigns were conducted. About 85 investigation teams including nearly 300 scientists participated, including forest ecologists and ecophysiologists, atmospheric physicists, boundary-layer meteorologists, hydrologists, biochemists, atmospheric chemists and remote sensing specialists.
The findings so far have been significant in terms of their implication for global change. The boreal ecosystem, occupying roughly 17 percent of the vegetated land surface and thus an important driver of global weather and climate, absorbs much more solar energy than is assumed by operational numerical weather prediction models. Albedo measurement show that this forest absorbs nearly 91% of the sun's incident energy. Additionally, while it is known that much of the boreal ecosystems consists of forested wetlands, lakes, bogs and fens, the measurements show that the atmosphere above was extremely dry; humidity and deep boundary layer convection (3,000 m) mimicked conditions found only over deserts. Physiological measurements of the trees show that this atmospheric desiccation was a result of the forests' strong biological control limiting surface evaporation. This tight control was linked to the low soil temperature and subsequently reduced rates of photosynthesis. BOREAS measurement also focused on net ecosystem carbon exchange. Data acquired during the late spring and summer, showed the boreal forests to be a net carbon sink. However, no measurements were taken in the early spring following thaw, and in the late fall, where the balance between photosynthesis and respiration is poorly understood. During 1996 additional data will be acquired to resolve the annual carbon budget and how it might depend on interannual climate differences.
A model for the succession of the forest ecosystem is described. The growth and development of trees and ground cover are controlled by temperature and light conditions and the availability of nitrogen and water. In addition, the effects of the annual cycle of trees including the risk of frost damage, wild fire, and wind damages are contained in the model as factors which control the survival and productivity of trees. The model also makes it possible to evaluated the risk of insect attack assuming that this risk is inversely related to the growth efficiency of trees.
The PDF includes an abstract in Finnish.
The article examines the problems of interdisciplinary research and the Finnish participation in MAB Project 2, which concentrates on the influences of man’s activities on forests. From the Finnish point of view, the main research areas are the effects of forestry activities which affect large areas, multiple use of forests, forests and environmental pollution, and the effects of energy economy.
This paper was presented in the ‘Man and the Biosphere’ programme project 2 seminar held on August 24–25 1978 in Hyytiälä research station of University of Helsinki.
The PDF includes a summary in English.
Man and the Biosphere (MAB) programme of UNESCO was launched in 1970. This interdisciplinary programme represents a new integrated approach to research, training and action aimed at improving man’s partnership with the environment. It consists of 14 project areas.
The Academy of Finland and the Finnish Committee for the MAB, in cooperation with the University of Helsinki and the city of Tampere organized a seminar with an aim of reviewing the execution of the Finnish participation in the MAB project No. 2. The seminar took place at Hyytiälä, a forest research station of the University of Helsinki, on August 24–25 1978.
During the seminar, an excursion was made to Pyynikki esker, a unique natural park close to the centre of the city of Tamper. Eight papers were presented and discussed in the seminar. The papers are published in this issue of Silva Fennica.
The PDF includes a summary in English.
In the article some aspects concerning the measurement of environmental factors are discussed. Special attention is given to the following questions: The correct way of determining the active surface in a forest ecosystem, the time factor in measurement processes, and the mutual correlative relationships between the environmental factors. Analysis of the data is also taken into consideration.
The PDF includes a summary in English.
The paper is a review on the topics of Symposium on forest types and forest ecosystems, held in connection to the IX internal botanical congress in Montreal in August 1959, the chairman of which was Ilmari Hustich. The article includes 18 preparatory papers that were distributed among the participants of the symposium. The common theme of the papers was the question of finding common platform for the different schools of forest types and forest ecosystems. In addition to the papers, the article includes a summary of the proceedings and discussions of the symposium.
The following papers were presented in the symposium:
Aichinger, E. Können wir eine gemeinsame Platform für die verscheidenen Schulen in der Waldtypenklassifikationen finden?
Arnborg, T. Can we find a common platform for the different schools of forest type classifications?
Dansereau, P. A combined structural and floristic approach to the definition of forest ecosystems.
Daubenmire, R. Some major problems in vegetation classification
Ellenberg, H. Können wir eine gemeinsame Platform für die verscheidenen Schulen in der Waldtypenklassifikationen finden?
Hills, G.A. Comparison of forest ecosystems (vegetation and soil) in different climatic zones
Kalela, A. Classification of the vegetation, especially of the forest, with particular reference to regional problems
Krajina, V.J. Can we find a common platform for the different schools of forest type classifications?
Kühler, A.W. Mapping tropical forest vegetation
Linteau, A. Y. a-t-il. Un terrain d’entente possible entre les différentes écoles au sujet de la classification de types forestiers?
Medvecka-Kornaś, A. Some problems of forest climaxes in Poland
Ovington, J.D. The ecosystem concept as aid to forest classification
Puri, G.S. The concept of climax in forest botany as applied in India
Rowe, J.S. Can we find a common platform for the different schools of forest type classifications?
Scamoni, A. Können wir eine gemeinsame Grundlage für die verscheidenen Schulen in der Waldtypenklassifikationen finden?
Sukachev, V.N. The correlation between the concept ’forest ecosystem’ and ’forest biogeocoenise’ and their importance for the classification of forests
Webb, L.J. A new attempt to classify Australian rain forest